HashtableOfInt


1   /*******************************************************************************
2    * Copyright (c) 2000, 2006 IBM Corporation and others.
3    * All rights reserved. This program and the accompanying materials
4    * are made available under the terms of the Eclipse Public License v1.0
5    * which accompanies this distribution, and is available at
6    * http://www.eclipse.org/legal/epl-v10.html
7    *
8    * Contributors:
9    *     IBM Corporation - initial API and implementation
10   *******************************************************************************/
11  package org.eclipse.jdt.internal.compiler.util;
12   
13   /**
14    * Hashtable for non-zero int keys.
15    */
16    
17  public final class HashtableOfInt {
18      // to avoid using Enumerations, walk the individual tables skipping nulls
19      public int[] keyTable;
20      public Object  [] valueTable;
21  
22      public int elementSize; // number of elements in the table
23      int threshold;
24  public HashtableOfInt() {
25      this(13);
26  }
27  public HashtableOfInt(int size) {
28      this.elementSize = 0;
29      this.threshold = size; // size represents the expected number of elements
30      int extraRoom = (int) (size * 1.75f);
31      if (this.threshold == extraRoom)
32          extraRoom++;
33      this.keyTable = new int[extraRoom];
34      this.valueTable = new Object  [extraRoom];
35  }
36  public boolean containsKey(int key) {
37      int length = keyTable.length, index = key % length;
38      int currentKey;
39      while ((currentKey = keyTable[index]) != 0) {
40          if (currentKey == key)
41              return true;
42          if (++index == length) {
43              index = 0;
44          }
45      }
46      return false;
47  }
48  public Object   get(int key) {
49      int length = keyTable.length, index = key % length;
50      int currentKey;
51      while ((currentKey = keyTable[index]) != 0) {
52          if (currentKey == key)  return valueTable[index];
53          if (++index == length) {
54              index = 0;
55          }
56      }
57      return null;
58  }
59  public Object   put(int key, Object   value) {
60      int length = keyTable.length, index = key % length;
61      int currentKey;
62      while ((currentKey = keyTable[index]) != 0) {
63          if (currentKey == key)  return valueTable[index] = value;
64          if (++index == length) {
65              index = 0;
66          }
67      }
68      keyTable[index] = key;
69      valueTable[index] = value;
70  
71      // assumes the threshold is never equal to the size of the table
72      if (++elementSize > threshold)
73          rehash();
74      return value;
75  }
76  private void rehash() {
77      HashtableOfInt newHashtable = new HashtableOfInt(elementSize * 2); // double the number of expected elements
78      int currentKey;
79      for (int i = keyTable.length; --i >= 0;)
80          if ((currentKey = keyTable[i]) != 0)
81              newHashtable.put(currentKey, valueTable[i]);
82  
83      this.keyTable = newHashtable.keyTable;
84      this.valueTable = newHashtable.valueTable;
85      this.threshold = newHashtable.threshold;
86  }
87  public int size() {
88      return elementSize;
89  }
90  public String   toString() {
91      String   s = ""; //$NON-NLS-1$
92      Object   object;
93      for (int i = 0, length = valueTable.length; i < length; i++)
94          if ((object = valueTable[i]) != null)
95              s += keyTable[i] + " -> " + object.toString() + "\n"; //$NON-NLS-2$ //$NON-NLS-1$
96      return s;
97  }
98  }
99
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